Spinal fixation system and method

ABSTRACT

A spinal fixation system includes a first plate, a post fixedly attached to the first plate and extending transverse therefrom. A second plate receives the distal end of the post. A locking mechanism is configured to restrict at least one of axial translation and/or orbital rotation of the second plate with respect to the post. The locking mechanism can include a locking nut having two non-concentric cylinders which enable an interference fit between the nut and the post, thus restricting axial translation of the second plate.

TECHNICAL FIELD

The present disclosure generally relates to medical devices for thetreatment of musculoskeletal disorders surgery, and more particularly toa surgical system and method for correction of a spine disorder.

BACKGROUND

Spinal pathologies and disorders such as scoliosis and other curvatureabnormalities, kyphosis, degenerative disc disease, disc herniation,osteoporosis, spondylolisthesis, stenosis, tumor, and fracture mayresult from factors including trauma, disease and degenerativeconditions caused by injury and aging. Spinal disorders typically resultin symptoms including deformity, pain, nerve damage, and partial orcomplete loss of mobility.

Non-surgical treatments, such as medication, rehabilitation and exercisecan be effective, however, may fail to relieve the symptoms associatedwith these disorders. Surgical treatment of these spinal disordersincludes correction, fusion, fixation, discectomy, laminectomy andimplantable prosthetics. Correction treatments used for positioning andalignment may employ implants, such as fixation devices, forstabilization of a treated section of a spine. This disclosure describesan improvement over these prior art technologies.

SUMMARY

Accordingly, a surgical system and method for correction of a spinedisorder is provided. In one embodiment, in accordance with theprinciples of the present disclosure, the spinal fixation systemincludes a first plate configured to be positioned between spinalprocesses of two adjacent vertebrae, and a post having one end fixedlyattached to the first plate and a distal second end. A second plate ispositioned opposite said first plate and configured to receive thedistal end of the post. The second plate can be axially translated alongthe post to a desired position.

According to another embodiment, in accordance with the principles ofthe present disclosure, the spinal fixation system includes a firstplate configured to be positioned on one side of two spinal processes oftwo adjacent vertebrae, and a post having one end fixedly attached tothe first plate and a distal second end. A second plate is positioned onan opposite side of the two spinal processes and is configured toreceive the distal end of the post. The second plate being capable of atleast axial translation along the post. A locking mechanism cooperativewith the post and the second plate locks and restricts at least one ofaxial translation and orbital rotation of the second plate with respectto the post.

In one embodiment, a method for correction of a spine disorder isprovided. The method comprises the steps of: providing access to asurgical site at a selected section of a spine; providing a spinalfixation system including a first plate configured to be positioned onone side of two spinal processes of two adjacent vertebrae and a posthaving one end fixedly attached to the first plate and a distal secondend. A second plate is positioned on an opposite side of the two spinalprocesses and is configured to receive the distal end of the post. Thesecond plate being capable of at least axial translation along the post.A locking mechanism cooperates with the post and the second plate tolock and restrict at least one of axial translation and orbital rotationof the second plate with respect to the post. The method furtherincluding positioning the first plate against the two spinal processes;positioning the second plate onto the post; adjusting an axial positionof the second plate along the post; adjusting an orbital rotationposition of the second plate with respect to said post; and locking theaxial translation and orbital rotation position using the lockingmechanism.

While multiple embodiments are disclosed, still other embodiments of thepresent application will become apparent to those skilled in the artfrom the following detailed description, which is to be read inconnection with the accompanying drawings. As will be apparent, thepresent disclosure is capable of modifications in various obviousaspects, all without departing from the spirit and scope of the presentdisclosure. Accordingly, the detailed description is to be regarded asillustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more readily apparent from thespecific description accompanied by the following drawings, in which:

FIG. 1 is a posterior view of one embodiment of the components of theInterspinous process plate fixation device according to the principlesof the present disclosure;

FIG. 2 is a cross sectional view of one embodiment of the Interspinousprocess plate fixation device shown FIG. 1 according to the principlesof the present disclosure;

FIG. 3 is a cross sectional view of another embodiment of theInterspinous process plate fixation device shown FIG. 1 according to theprinciples of the present disclosure;

FIG. 4 is a cross sectional view of yet another embodiment of theInterspinous process plate fixation device shown FIG. 1 according to theprinciples of the present disclosure;

FIG. 5A is a cross-sectional view of a further embodiment of theInterspinous process plate fixation device showing a locking featureaccording to the principles of the present disclosure;

FIG. 5B is an enlarged cross sectional view of the locking feature shownin FIG. 5A in an unlocked position;

FIG. 5C is an enlarged cross sectional view of the locking feature shownin FIG. 5A in a locked position;

FIG. 6 is a cross-sectional view of yet a further embodiment of theInterspinous process plate fixation device showing an alternativelocking feature according to the principles of the present disclosure;

FIG. 7A is an end view of an embodiment of a locking nut used with thelocking feature of the Interspinous process plate fixation deviceaccording to the principles of the present disclosure;

FIG. 7B is a side view of the locking nut shown in FIG. 7A;

FIG. 7C is a side, cross sectional view of the locking nut shown in FIG.7A;

FIG. 8 is a cross-sectional view of an embodiment of the locking featureof the Interspinous process plate fixation device showing use of thelocking nut of FIGS. 7A-7C; and

FIG. 9 is a perspective, cross-sectional view of a further embodiment ofthe Interspinous process plate fixation device showing anotheralternative locking feature according to the principles of the presentdisclosure; and

FIG. 10 is a side, cross-sectional view of the Interspinous processplate fixation device shown in FIG. 9.

Like reference numerals indicate similar parts throughout the figures.

DETAILED DESCRIPTION

The exemplary embodiments of the surgical system and related methods ofuse disclosed are discussed in terms of medical devices for thetreatment of musculoskeletal disorders and more particularly, in termsof a surgical system and method for correction of a spine disorder. Itis envisioned that the surgical system and method may be employed inapplications such as correction of deformities such as kyphosis,scoliosis. For example, the surgical system and method can include anInterspinous process plate fixation device.

According to one aspect, this disclosure involves an Interspinousprocess plate fixation device configured for surgical implantation at abone site. In some embodiments, the fixation device is provided which isspecifically designed to fuse two adjacent interspinous processes and/orlamina. For example, one embodiment involves two plates positioned onopposing sides of spinal processes and a post adjustablyconnecting/securing the two plates to each other. A locking nutconfigured to be received by the post can allow for both orbital motionand translation of the fixation device.

It is contemplated that one or all of the components of the surgicalsystem may be disposable, peel-pack, pre-packed sterile devices. One orall of the components of the surgical system may be reusable. Thesurgical system may be configured as a kit with multiple sized andconfigured components.

It is envisioned that the present disclosure may be employed to treatspinal disorders such as, for example, degenerative disc disease, discherniation, osteoporosis, spondylolisthesis, stenosis, scoliosis andother curvature abnormalities, kyphosis, tumor and fractures. It iscontemplated that the present disclosure may be employed with otherosteal and bone related applications, including those associated withdiagnostics and therapeutics. It is further contemplated that thedisclosed surgical system and methods may be alternatively employed in asurgical treatment with a patient in a prone or supine position, and/oremploy various surgical approaches to the spine, including anterior,posterior, posterior mid-line, direct lateral, postero-lateral, and/orantero-lateral approaches, and in other body regions. The presentdisclosure may also be alternatively employed with procedures fortreating the lumbar, cervical, thoracic and pelvic regions of a spinalcolumn. The system and methods of the present disclosure may also beused on animals, bone models and other non-living substrates, such as,for example, in training, testing and demonstration.

The present disclosure may be understood more readily by reference tothe following detailed description of the disclosure taken in connectionwith the accompanying drawing figures, which form a part of thisdisclosure. It is to be understood that this disclosure is not limitedto the specific devices, methods, conditions or parameters describedand/or shown herein, and that the terminology used herein is for thepurpose of describing particular embodiments by way of example only andis not intended to be limiting of the claimed disclosure. Also, as usedin the specification and including the appended claims, the singularforms “a,” “an,” and “the” include the plural, and reference to aparticular numerical value includes at least that particular value,unless the context clearly dictates otherwise. Ranges may be expressedherein as from “about” or “approximately” one particular value and/or to“about” or “approximately” another particular value. When such a rangeis expressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment. It isalso understood that all spatial references, such as, for example,horizontal, vertical, top, upper, lower, bottom, left and right, are forillustrative purposes only and can be varied within the scope of thedisclosure. For example, the references “upper” and “lower” are relativeand used only in the context to the other, and are not necessarily“superior” and “inferior”.

Further, as used in the specification and including the appended claims,“treating” or “treatment” of a disease or condition refers to performinga procedure that may include administering one or more drugs to apatient (human, normal or otherwise or other mammal), in an effort toalleviate signs or symptoms of the disease or condition. Alleviation canoccur prior to signs or symptoms of the disease or condition appearing,as well as after their appearance. Thus, treating or treatment includespreventing or prevention of disease or undesirable condition (e.g.,preventing the disease from occurring in a patient, who may bepredisposed to the disease but has not yet been diagnosed as having it).In addition, treating or treatment does not require complete alleviationof signs or symptoms, does not require a cure, and specifically includesprocedures that have only a marginal effect on the patient. Treatmentcan include inhibiting the disease, e.g., arresting its development, orrelieving the disease, e.g., causing regression of the disease. Forexample, treatment can include reducing acute or chronic inflammation;alleviating pain and mitigating and inducing re-growth of new ligament,bone and other tissues; as an adjunct in surgery; and/or any repairprocedure. Also, as used in the specification and including the appendedclaims, the term “tissue” includes soft tissue, ligaments, tendons,cartilage and/or bone unless specifically referred to otherwise.

The components of Interspinous process plate fixation device 10 can befabricated from biologically acceptable materials suitable for medicalapplications, including metals, synthetic polymers, ceramics and bonematerial and/or their composites, depending on the particularapplication and/or preference of a medical practitioner. For example,the components of Interspinous process plate fixation device 10,individually or collectively, can be fabricated from materials such asstainless steel alloys, commercially pure titanium, titanium alloys,Grade 5 titanium, super-elastic titanium alloys, cobalt-chrome alloys,stainless steel alloys, superelastic metallic alloys (e.g., Nitinol,super elasto-plastic metals, such as GUM METAL® manufactured by ToyotaMaterial Incorporated of Japan), ceramics and composites thereof such ascalcium phosphate (e.g., SKELITE™ manufactured by Biologix Inc.),thermoplastics such as polyaryletherketone (PAEK) includingpolyetheretherketone (PEEK), polyetherketoneketone (PEKK) andpolyetherketone (PEK), carbon-PEEK composites, PEEK-BaSO₄ polymericrubbers, polyethylene terephthalate (PET), fabric, silicone,polyurethane, silicone-polyurethane copolymers, polymeric rubbers,polyolefin rubbers, hydrogels, semi-rigid and rigid materials,elastomers, rubbers, thermoplastic elastomers, thermoset elastomers,elastomeric composites, rigid polymers including polyphenylene,polyamide, polyimide, polyetherimide, polyethylene, epoxy, bone materialincluding autograft, allograft, xenograft or transgenic cortical and/orcorticocancellous bone, and tissue growth or differentiation factors,partially resorbable materials, such as, for example, composites ofmetals and calcium-based ceramics, composites of PEEK and calcium basedceramics, composites of PEEK with resorbable polymers, totallyresorbable materials, such as, for example, calcium based ceramics suchas calcium phosphate, tri-calcium phosphate (TCP), hydroxyapatite(HA)-TCP, calcium sulfate, or other resorbable polymers such aspolyaetide, polyglycolide, polytyrosine carbonate, polycaroplaetohe andtheir combinations. Various components of correction system 10 may havematerial composites, including the above materials, to achieve variousdesired characteristics such as strength, rigidity, elasticity,compliance, biomechanical performance, durability and radiolucency orimaging preference. The components of Interspinous process platefixation device 10, individually or collectively, may also be fabricatedfrom a heterogeneous material such as a combination of two or more ofthe above-described materials. The components of Interspinous processplate fixation device 10 may be monolithically formed, integrallyconnected or include fastening elements and/or instruments, as describedherein.

Interspinous process plate fixation device 10 is employed, for example,with an open, mini-open or minimally invasive surgical technique toprovide stabilization of a spine or other musculoskeletal structure. Inpreferred embodiments, the Interspinous process plate fixation device 10is configured to be integrated with instrumentation to allow for onehand insertion and implantation to stabilize two adjacent vertebrae forany surgical procedure requiring the same.

In one embodiment, the system includes a first plate configured to bepositioned between spinal processes of two adjacent vertebrae and a posthaving one end fixedly attached to the first plate and a distal secondend. The system also includes a second plate positioned opposite thefirst plate and configured to receive the distal end of the post in aconfiguration that the second plate is capable of at least axialtranslation along the post.

In another embodiment a method for correction of a spine disorder, usingthe system of the disclosure is provided. The method comprises the stepsof: providing access to a surgical site at a selected section of aspine; providing a spinal fixation system according to the disclosureincluding a first plate configured to be positioned on one side of twospinal processes of two adjacent vertebrae and a post having one endfixedly attached to the first plate and a distal second end. The systemalso includes a second plate positioned on an opposite side of the twospinal processes and being configured to receive the distal end of thepost. The second plate is configured so as to at least axially translatealong the post. A locking mechanism cooperative with the post and thesecond plate is provided to lock and restrict at least one of axialtranslation and orbital rotation of the second plate with respect to thepost.

The method also includes positioning the first plate against the twospinal processes and positioning the second plate onto the post. Once inposition, adjusting an axial position of the second plate along the postand adjusting an orbital rotation position of the second plate withrespect to said post so as to arrive at the proper placement. Onceproperly placed, the axial translation and orbital rotation position islocked using the locking mechanism. The following discussion includes adescription of a surgical system and related methods of employing thesurgical system in accordance with the principles of the presentdisclosure. Alternate embodiments are also disclosed. Reference will nowbe made in detail to the exemplary embodiments of the presentdisclosure, which are illustrated in the accompanying figures.

Turning now to FIGS. 1-10, there is illustrated components of a surgicalsystem, such as, for example, an interspinous process plate fixationdevice 10 in accordance with the principles of the present disclosure.

Referring to FIG. 1, Interspinous process plate fixation device 10includes a first or head plate 12 configured to provide fixation withvertebrae along an axial or longitudinal direction of the spine. Asecond or locking plate 14 is provided that is connected to the plate 12by a post 16. Second plate 14 is also configured to provide fixationwith vertebrae along an axial or longitudinal direction of the spine. Inthe example of FIG. 1, the plates 12 and 14 of the fixation device 10are shown attached to processes SP-L4 and SP-L5 of vertebrae L4 and L5,respectively, however it is understood that the present principles arenot limited to this level of fixation only and is contemplated toprovide restricted motion to all motion segments of the spine whereapplicable.

The plates 12 and 14 may include various cross sections, such as, e.g.,oval, polygonal, U-shaped, irregular, uniform, non-uniform, variable,tapered, etc. as needed or desired. It is further envisioned that plate12 and plate 14 may include a uniform thickness/diameter or may havevarious other configurations. In addition, the plate 12 and plate 14 mayhave various surface finishes, such as, for example, rough, threaded forconnection with surgical instruments, arcuate, undulating, porous,semi-porous, dimpled, polished and/or textured according to therequirements of a particular application. It is contemplated that theshapes of the plates (12, 14) may be uniformly increasing or decreasing,or have alternate cross-section dimensions along their length. Further,plate 12 and plate 14 may have pre-defined curvatures (bends) alongtheir length in furtherance of a surgical goal for a particularapplication.

The post 16 may include various cross sections, such as cylindrical,square, triangular, hexagonal, or any other geometrical cross sectionalfor which the plates and locking mechanisms are configured.

Referring to FIGS. 1 and 2, plate 12 is connected to post 16 by aconnection mechanism 18. Connection mechanism 18 extends from theinboard face of plate 12 and does not allow for orbital rotation ortranslation once plate 12 and post 16 are adjoined together. Examples ofconnection mechanisms 18 for fixedly connecting plate 12 to post 16 canbe, for example, via retaining ring, setscrew, pin, clamp or welding.The plate 16 provides for translation 20 along the axis of post 16. Byway of example, the means for translation 20 can include a taperedcollet 22 around post 16 and having an angular or tapered surface 23that cooperates with a correspondingly angled or tapered inside orinboard surface 24 of plate 14, and through the axial movement of collet22 toward plate 12, functions to lock the axial translation of plate 14with respect to post 16. Plate 12 and 14 will often include spikes 13and 15, respectively for engaging the spinal processes when the platesare locked into their operable fixation position.

The details of the locking mean 26 of the translation is explained ingreater detail below with respect to FIGS. 5-10. The range of angles forthe angular or tapered surface 23 of the means for translation 22 andthe corresponding angular surface 24 of plate 14, could be, for examplewithin the range of 1°-45° with respect to the central axis of post 16.

Referring to FIG. 3, there is shown a cross section of anotherembodiment of the Interspinous process plate fixation device. In thisembodiment, plate 12 is fixedly connected 18 to post 16 that extendsfrom the inboard face of plate 12 and does not allow for orbitalrotation or translation once plate 12 and post 16 are adjoined together.Examples of means for connecting plate 12 to post 16 can be, forexample, via retaining ring, setscrew, pin, clamp or welding. The plate14 provides for translation 20 along the axis of post 16 and orbitalrotation 30 about a point on the axis of the post. By way of example,the means for translation 20 can include a tapered collet 22 around post16 and having an angular or tapered surface 23 that cooperates with acorrespondingly angled inside surface 33 of a spherical collar 32, andthrough the axial movement of collet 22 toward plate 12, functions tolock the axial translation of plate 14, via spherical collar 32, withrespect to post 16. The range of angles for the angular or taperedsurface 26 of the means for translation 22 and the corresponding angularsurface 24 of plate 14, could be, for example within the range of 1°-45°with respect to the central axis of post 16.

The means for orbital rotation 30 includes a spherical collar 32 havinga convex outer surface 34 that cooperates with a concave inner surface36 of plate 14, and an inner tapered or angular surface 33 that, asdescribed above, cooperates with the tapered collet 22. The lockingmechanism 38 included with plate 14 is described in more detail belowwith respect to FIGS. 5-10 below, and operates to lock the translationand/or orbital motion when plate 14 has been positioned and oriented asdesired for the particular fixation application.

FIG. 4 shows another embodiment of the Interspinous process platefixation device. In this implementation, both plates 12 and 14 areprovide for translation 20 along the axis of post 16 and orbitalrotation 30 about a point on the axis of the post 16. Both plates 12 and14 contain the locking mechanism 38 to restrict translation and orbitalrotation, or translation only.

FIGS. 5A-5C show an implementation of the orbital and translationallocking mechanism 26, 28 for the Interspinous process plate fixationdevice according to embodiments of the present principles. In oneexample, the tapered lock can be pressed into position so as to createan interference fit between the inside or inboard tapered surface 24 ofplate 14 and the tapered collet 22. The applied force to engage thetaper can occur by an instrument or the plate and collet can possessthreads where a nut can create the applied force to lock the device. Ascollet 22 is slid in between plate 14 and post 16, it wedges plate 14and post 16 together to lock plate 14 and post 16 in place. In oneembodiment, as shown in FIG. 5C, tapered collet 22 includes a snap 50feature which operates to prevent plate 14 and post 16 from slidingaround as tapered collet 22 is inserted.

As shown in FIGS. 5B, 5C and 6 snap 50 prevents plate 14 and post 16from sliding around as collet 22 is inserted. Spherical collar 32 ispressed into position so as to create the interference fit between theinside taper 33 of the spherical collar and the tapered collet 22. Thetapered collet 22 causes a frictional engagement of plate 14 and post16. The applied force to engage the taper can occur by instrument or thespherical collar 32 and tapered collet 22 can possess threads where anut can create the applied force to lock the fixation device. Thislocking feature 38 can restrict both translation and orbital motion ofthe plate 14. The spherical collar 32 includes a notch or slit 56 and asthe tapered collet 22 is pressed further into the plate (toward thespinal process) against the sphere's inside taper 33, the lockingfeature will expand and cause the interference fit between the outsideof the spherical collar 32 and the inside or inboard surface of plate14. In an alternative configuration, the notch or slit 56 can be removedfrom the inner surface of spherical collar 32, thus retaining theorbital motion capability after translational motion has beenrestricted.

Referring to FIGS. 7A-7C and 8, there is shown a locking nut 70according to another embodiment of the present principles. The lockingnut 70 has two cylinders, an inner cylinder 76 and an outer cylinder 77,and preferably has an off center axis 78 between the two cylinders, suchthat the two cylinders are non-concentric. The locking nut 70 isconfigured such that the inner 76 and outer 77 cylinders can be threadedto a position which will align their inside hole features (i.e., centralaxes) and allow the receiving of the post 16. Upon rotation of onecylinder with respect to the other via distal nut 74, the non-concentricdesign of the cylinders will create an interference fit between bothcylinders and the post. The outside cylinder 77 may or may not include abreak off feature 73 to control applied torque (via distal nut 74) tolock the device onto the post. An outside cylinder removal nut 72 can beused for disengagement of the locking nut 70. This locking nut 70feature can be used to restrict translation of the plate along the post16. The inner threaded shaft of inner cylinder 76 is preferably keyed tothe center post 16 so as to allow translation movement (before locking),but does not allow any rotation or orbital motion.

A spherical tip 80 on the outer cylinder not only provides anarticulating surface between the tip and a correspondingly shapedsurface 84 on the outboard surface of plate 14, but also functions toallow the plate 14 to orbit about a fixed point on the axis of the post16. As will be evident from the drawing, the two non-concentric holes 82of the inner cylinder 76 and the outer cylinder 77, as twisted, willlock onto the shaft/post 16, thus restricting any translational motionof the plate 14 with respect to the post 16.

In an alternative configuration, the inside cylinder 76 may be affixedto the outboard surface of plate 14 and the outside cylinder 77 of nut72 is threaded away from the plate to lock the device. In thisembodiment, locking of the locking nut 70 would restrict both orbitalmotion and translational motion of the plate.

FIGS. 9 and 10 show two different embodiments of a two-piecenon-concentric/off center axes locking nut according to the presentprinciples. Referring to FIG. 8 there is shown a locking nut 90 whichcan be twisted to a position that will align the two inside holefeatures of the two respective components (spherical end 101 and outerspherical feature 103) to allow insertion and smooth translation ofplate 14 with respect to post 16. Nut 90 has a spherical end 101 whichengages with an outer spherical feature 103. As with the embodiment ofFIGS. 7-9, the holes in spherical end 101 and feature 103 arenon-concentric 102, thus when operating in combination, the twisting ofthe distal hex nut 94 will rotate the two axes of the respective partsout of alignment to create an interference fit between the two piecelocking nut 90 which will expand the locking nut and grip the inside ofthe plate 14 and post 16. The locking nut 90 may or may not include abreak off feature 93 to control applied torque to lock the device ontothe post. The proximal hex nut 92 can be used for disengagement of thelocking nut. The articulating surface 100 of the tip of the outerspherical feature 107 of nut 90, and corresponding inside surface of theplate 14, in combination of with the twisting action of the twonon-concentric holes (designated at 102) of the respective cylinders canrestrict the translation of the plate along the post 16. According toone alternative configuration, the outer spherical feature 103 in thisconfiguration can be slit 104 to allow expansion and interference withinthe plate 14 to lock both orbital and translational motion.

Alternatively, as shown in FIG. 10, the outer sphere 107 is not splitand is integrated with nut 92 such that when twisting the outer cylindervia proximal hex nut 92, the non-concentric holes 102 in the innercylinder 106 and outer spherical feature 107 will rotate the two axesout of alignment and create the interference, via articulating surface100, and the engagement of the inner cylinder 106 with the post 16,caused by the outer spherical feature 107.

In one embodiment, fixation system 10 may be treated with or include anagent, which may be disposed, packed or layered within, on or about thecomponents and/or surfaces of system 10. It is envisioned that the agentmay include bone growth promoting material, such as, for example, bonegraft to enhance fixation of the fixation device 10 with spinalprocesses of vertebrae.

It is contemplated that the agent may include therapeuticpolynucleotides or polypeptides. It is further contemplated that theagent may include biocompatible materials, such as, for example,biocompatible metals and/or rigid polymers, such as, titanium elements,metal powders of titanium or titanium compositions, sterile bonematerials, such as allograft or xenograft materials, synthetic bonematerials such as coral and calcium compositions, such as HA, calciumphosphate and calcium sulfite, biologically active agents, for example,gradual release compositions such as by blending in a bioresorbablepolymer that releases the biologically active agent or agents in anappropriate time dependent fashion as the polymer degrades within thepatient. Suitable biologically active agents include, for example, BMP,Growth and Differentiation Factors proteins (GDF) and cytokines. Thecomponents of fixation system 10 can be made of radiolucent materialssuch as polymers. Radiomarkers may be included for identification underx-ray, fluoroscopy, CT or other imaging techniques. It is envisionedthat the agent may include one or a plurality of therapeutic agentsand/or pharmacological agents for release, including sustained release,to treat, for example, pain, inflammation and degeneration.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplification of thevarious embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1-20. (canceled)
 21. A spinal fixation system, comprising: a first platecomprising a first end configured to engage a spinous process of a firstvertebra and a second end configured to engage a spinous process of asecond vertebra; a post comprising a first end coupled to the firstplate and a second end; and a second plate comprising a first endconfigured to engage the spinous process of the first vertebra and asecond end configured to engage the spinous process of the secondvertebra, the second plate comprising an opening positioned between thefirst and second ends of the second plate, the opening having the secondend of the post disposed therein such that the second plate is rotatablerelative to the first plate.
 22. A system as recited in claim 21,wherein the first plate is axially fixed relative to the post such thatthe first plate is prevented from moving relative to the post along alongitudinal axis defined by the post.
 23. A system as recited in claim21, wherein the post is rotatable relative to the first plate about alongitudinal axis defined by the post.
 24. A system as recited in claim21, wherein the second plate is configured to translate axially relativeto the first plate along a longitudinal axis defined by the post.
 25. Asystem as recited in claim 21, wherein the second plate is rotatablerelative to the post in a plurality of planes.
 26. A system as recitedin claim 21, wherein the first plate comprises an opening positionedbetween the first and second ends of the first plate, the first end ofthe post being disposed in the opening in the first plate.
 27. A systemaccording to claim 26, wherein the post is retained within the openingin the first plate by a retaining ring.
 28. A system according to claim26, wherein the opening in the first plate is coaxial with the openingin the second plate.
 29. A system according to claim 21, furthercomprising a nut positioned within the opening in the second plate, thenut comprising an aperture extending therethrough, the second end of thepost being positioned within the aperture.
 30. A system according toclaim 29, wherein the nut comprises a spherical outer surface thatengages an arcuate inner surface of the second plate that defines theopening in the second plate such that the nut is rotatable relative tothe second plate.
 31. A system according to claim 29, wherein the nutcomprises a slit.
 32. A system according to claim 29, wherein the secondend of the post extends completely through the aperture.
 33. A systemaccording to claim 29, wherein the post is movable relative to thesecond plate between a first configuration in which a first length ofthe post extends outwardly from the nut and a second configuration inwhich an increased second length of the post extends outwardly from thenut.
 34. A system as recited in claim 33, wherein the first plate isspaced apart from the second plate by a first distance when the post isin the first configuration and is spaced apart from the second plate bya reduced second distance when the post is in the second configuration.35. A system as recited in claim 21, wherein an inner surface of thefirst plate faces an inner surface of the second plate, the innersurfaces each including a plurality of spikes extending outwardlytherefrom.
 36. A system as recited in claim 21, wherein the second platecomprises an intermediate portion between the first and second ends ofthe second plate, the intermediate portion comprising the opening in thesecond plate, the second plate being free of any openings between theintermediate portion and the first end of the second plate and betweenthe intermediate portion and the second end of the second plate.
 37. Asystem as recited in claim 21, wherein the first end of the post isremovably coupled to the first plate.
 38. A system as recited in claim21, wherein the first and second plates each have pre-defined bendsalong their lengths.
 39. A method for correction of a spinal disorder,comprising: providing the spinal fixation system recited in claim 21;engaging the first end of the first plate with a first side of the firstvertebra and engaging the second end of the first plate with a firstside of the second vertebra; rotating the second plate relative to thepost to position the second plate in a selected orientation; andtranslating the second plate relative to the first plate along the postsuch that the second plate moves toward the first plate and the firstend of the second plate engages a second side of the first vertebra andthe second end of the second plate engages a second side of the secondvertebra.
 40. A method as recited in claim 39, wherein: a nut ispositioned within the opening in the second plate, the nut comprising anaperture extending therethrough, the second end of the post beingpositioned within the aperture; and rotating the second plate comprisesrotating the second plate about the nut while the nut is provisionallyfixed relative to the post.